1. Technical Field
The present invention relates to a carbon dioxide recovery system for removing and recovering carbon dioxide contained in a combustion exhaust gas of a boiler in a thermal power plant, a power generation system using the carbon dioxide recovery system, and a method for these systems.
2. Background Art
In a power generation system of a thermal power plant using a large amount of fossil fuel, an amine absorption method is adopted as a method for removing and recovering carbon dioxide (CO2) which is one of the causes of global warming. The amine absorption method has a problem that the large energy consumption at the time of separating and recovering CO2 from a loaded absorption liquid with CO2 absorbed therein significantly lowers the power generation output.
For example, in Japanese Patent Laid-Open No. 3-193116, as shown in FIG. 4A, there is proposed a configuration in which a reboiler 41 is provided for a tower bottom part of a regeneration tower 24 for regenerating a loaded absorption liquid with CO2 absorbed therein, and in which high pressure steam of about 3 kg/cm2 absolute pressure is extracted from a low pressure turbine 8 and is supplied to the reboiler 41 provided for the bottom part of the regeneration tower as a heating source. This enables the loaded absorption liquid of the tower bottom part to be heated to an absorption liquid regeneration temperature of about 110 to 130° C., and hence, CO2 in the loaded absorption liquid is separated so that the absorption liquid is regenerated. However, when all thermal energy required for the reboiler 41 of the tower bottom part is supplemented by the steam extracted from the low pressure turbine 8, the amount of the steam extracted from the low pressure turbine 8 becomes large, which causes a problem that the output of the low pressure turbine 8 is significantly lowered and the power generation output is reduced.